I'm not quite sure what you are having trouble with exactly. I put the excel file into a zip container (GTP doesn't allow for .xls files to be uploaded). And I tested the file by downloading it and checking it. It's working on my end.
To alleviate the problem, I'm uploading a second copy of the template as a pdf document. GTP allows PDFs in as direct uploads.
The PDF version is able to be filled out as a form. It allows you to check off mods you have installed as well as enter in the data for tuning settings. This was just a quick conversion so there are likely some rough edges, but it works.
https://www.gtplanet.net/forum/showthread.php?t=141752#post4304919
I'll also include an example (my Lancia Stratos setup) to show how it can be used.